Epicyclic gear mechanism for multiple input/output systems

ABSTRACT

Methods and systems for an epicyclic gear mechanism that includes a primary differential assembly to selectively drive the fore secondary differential assembly and the aft secondary differential assembly. The fore secondary differential assembly selectively drives one or more fore interfaces (e.g., output gears), whereas the aft secondary differential assembly selectively drives one or more aft interfaces (e.g., output gears). Each of the primary differential assembly, the fore and aft secondary differential assemblies, and the interfaces rotate about a common central axis. The primary differential assembly drives the fore secondary differential assembly via a first sun gear, and drives the aft secondary differential assembly via a second sun gear, both of which rotate about the common central axis. Further, one or more actuators are to activate or deactivate in order to drive or be driven by a selected interface.

PRIORITY CLAIM/INCORPORATION BY REFERENCE

N/A

FIELD

Certain embodiments of the disclosure relate to an epicyclic gearmechanism for multiple input/output systems. More specifically, certainembodiments of the disclosure relate to an epicyclic gear mechanism thatincludes a primary differential assembly to selectively drive one ormore secondary differential assemblies, each of which may selectivelydrive one or more interfaces. Advantageously, these differentialassemblies and interfaces rotate about a single common axis.

BACKGROUND

Existing multi-branch gear designs, which do not rotate about a commoncentral axis, are costly, heavy, and take valuable space in systems inwhich they are deployed.

Further limitations and disadvantages of conventional and traditionalapproaches will become apparent to one of skill in the art, throughcomparison of such systems with the present disclosure as set forth inthe remainder of the present application with reference to the drawings.

BRIEF SUMMARY

A system and/or method is provided for an epicyclic gear mechanism todrive multiple outputs. In an example, an epicyclic gear mechanismincludes a primary differential assembly to selectively drive a foresecondary differential assembly and an aft secondary differentialassembly. The fore secondary differential assembly selectively drivesone, more than one, or none of one or more fore interfaces, whereas theaft secondary differential assembly selectively drives one, more thanone, or none of one or more aft interfaces. Each of the primarydifferential assembly, the fore secondary differential assembly, the aftsecondary differential assembly and each of the primary, fore and aftinterfaces rotate about a common central axis.

The primary differential assembly drives the fore secondary differentialassembly via a first sun gear, and drives the aft secondary differentialassembly via a second sun gear, both of which rotate about the commoncentral axis. Further, one or more actuators are to activate ordeactivate in order to drive a selected fore or aft interface,substantially as shown in and/or described in connection with at leastone of the figures, as set forth more completely in the claims.

In disclosed examples, an epicyclic gear mechanism includes a foresecondary differential assembly to selectively drive one, more than one,or none of one or more fore interfaces. An aft secondary differentialassembly selectively drives one, more than one, or none of one or moreaft interfaces. A primary differential assembly selectively drives one,more than one, or none of the fore secondary differential assembly andthe aft secondary differential assembly, wherein the primarydifferential assembly, the fore secondary differential assembly, the aftsecondary differential assembly and each of the fore and aft interfacesrotate about a common central axis.

In some examples, one or more grounding mechanisms are included, eachgrounding mechanisms being configured to activate or deactivate acorresponding interface in response to a command.

In examples, the primary differential assembly is further configured todrive the fore secondary differential assembly via a first sun gear, andto drive the aft secondary differential assembly via a second sun gear.In some examples, the first sun gear and the second sun gear rotateabout the common central axis.

In examples, the primary differential assembly includes a carrier havinga primary interface configured to transfer torque to drive one or moreof the fore or aft secondary differential assemblies in response to amechanical input.

In some examples, the torque creates rotational movement of a primarycarrier of the primary differential assembly causing one or more planetgears within the primary carrier to turn, thereby causing rotation ofthe first and/or second sun gear.

In examples, a fore carrier of the fore secondary differential assemblyis in a fixed arrangement with the first sun gear, wherein one or moreplanet gears within the primary differential assembly are configured todrive the first sun gear causing rotation of the fore secondarydifferential assembly.

In some examples, the fore carrier includes one or more planet gearssuch that the rotational movement of the fore secondary differentialassembly about the common central axis selectively causes the one ormore planet gears to rotate about a planet shaft.

In examples, the one or more fore interfaces include one or more forering gears, the one or more planet gears within the fore carrier beingconfigured to mesh with an interior gear of the one or more fore ringgears.

In some examples, a shaft in a fixed arrangement with the second sungear is included, wherein one or more the planet gears within theprimary differential assembly are configured to cause rotation of theaft secondary differential assembly by driving the second sun gearcausing rotation of the shaft.

In examples, an aft carrier of the aft secondary differential assemblyis included, the aft carrier including one or more planet gears suchthat rotational movement of the shaft turns the aft carrier about thecommon central axis selectively causing the one or more planet gears torotate about a planet shaft.

In some examples, the one or more aft interfaces include one or more aftring gears, wherein the one or more planet gears within the aft carrierare configured to mesh with an interior gear of the one or more aft ringgears. In examples, the interfaces are one or more of a gear, a belt, ora roller chain and sprocket.

In disclosed examples, an epicyclic gear mechanism includes a primarydifferential assembly having a plurality of planet gears to transmitmotion to one, both or none of a first or a second sun gear, and aprimary carrier with a fixed primary gear, the primary gear configuredto transfer torque from a power source to the plurality of planet gears.A fore secondary differential assembly selectively driven by torque viathe first sun gear and configured to selectively drive one, more thanone, or none of one or more fore interfaces. An aft secondarydifferential assembly selectively driven by torque via the second sungear and configured to selectively drive one, more than one, or none ofone or more aft interface.

In some examples, the primary differential assembly, the fore secondarydifferential assembly, the aft secondary differential assembly and eachof the fore and aft interfaces rotate about a common central axis.

In examples, the first sun gear and the second sun gear rotate about thecommon central axis. In some examples, the first sun gear and the secondsun gear are arranged within the primary carrier.

In examples, a plurality of actuators are included to selectivelyactivate or deactivate the one or more interfaces. In some examples, aninterface selection device is included, wherein selection of a giveninterface activates a corresponding actuator to drive or be driven bythe selected interface. In examples, the actuator engages a brakingsystem corresponding to the selected interface. In some examples, thebraking system includes one or more of a grounding mechanism, anelectrically configurable brake or a mechanically configurable brake. Inexamples, the electrically configurable brake is actuated by applicationor removal of power to the electrically configurable brake, therebyengaging or disengaging the configurable brake. In some examples, themechanically configurable brake is actuated by application or removal ofa mechanical force including a linear force or a rotational force.

In disclosed examples, an epicyclic gear mechanism includes a primarydifferential assembly having a plurality of planet gears to transmitmotion to one, both or none of a first or a second sun gear, and aprimary carrier with a fixed primary gear, the primary gear configuredto transfer torque from a power source to the plurality of planet gears.A fore secondary differential assembly is selectively driven by torquevia the first sun gear and configured to selectively drive one, both ornone of a first and a second tertiary differential assembly. And an aftsecondary differential assembly selectively driven by torque via thesecond sun gear and configured to selectively drive one, both or none ofa third and a fourth tertiary differential assembly, wherein each of thetertiary differential assemblies is configured to selectively drive aplurality of output ring gears.

In some disclosed examples, an epicyclic gear mechanism includes a foresecondary differential assembly to selectively engage one, more thanone, or none of one or more fore interfaces. An aft secondarydifferential assembly selectively engages one, more than one, or none ofone or more aft interfaces. And a primary differential assembly toselectively engage one, more than one, or none of the fore secondarydifferential assembly and the aft secondary differential assembly,wherein an interface of the one or more fore or aft interfaces isconfigured to selectively receive mechanical power from a power sourceand transfer mechanical power to drive one or more of the other fore oraft interfaces, and wherein the primary differential assembly, the foresecondary differential assembly, the aft secondary differential assemblyand each of the fore and aft interfaces rotate about a common centralaxis.

In some examples, the other fore or aft interface transfers mechanicalpower to an external load.

In examples, the interface of the one or more fore or aft interfaces isconfigured to drive a primary interface of the primary differentialassembly.

These and various other advantages, aspects and novel features of thepresent disclosure, as well as details of an illustrated embodimentthereof, will be more fully understood from the following descriptionand drawings.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a perspective view of an epicyclic gear mechanism for multipleoutput systems, in accordance with an example embodiment of thedisclosure.

FIG. 2 is another perspective view of an epicyclic gear mechanism formultiple output systems, in accordance with an example embodiment of thedisclosure.

FIG. 3 is a lateral view of an epicyclic gear mechanism for multipleoutput systems, in accordance with an example embodiment of thedisclosure.

FIG. 4 illustrates a schematic of a four output branch differential geartrain of an epicyclic gear mechanism, in accordance with an exampleembodiment of the disclosure.

FIG. 5 is a perspective view of an epicyclic gear mechanism for multipleoutput systems including a mechanical power source, a powertransmission, and one or more output shafts and corresponding shaftinterfaces, in accordance with an example embodiment of the disclosure.

FIG. 6 illustrates a schematic of an eight output branch differentialgear train of an epicyclic gear mechanism, in accordance with an exampleembodiment of the disclosure.

FIG. 7 illustrates a schematic of an electromechanical actuator controlsystem for an epicyclic gear mechanism for multiple output systems, inaccordance with an example embodiment of the disclosure.

The figures are not necessarily to scale. Where appropriate, similar oridentical reference numbers are used to refer to similar or identicalcomponents.

DETAILED DESCRIPTION

As utilized herein, “and/or” means any one or more of the items in thelist joined by “and/or”. For example, “x and/or y” means any element ofthe three-element set {(x), (y), (x, y)}. Similarly, “x, y, and/or z”means any element of the seven-element set {(x), (y), (z), (x, y), (x,z), (y, z), (x, y, z)}. As utilized herein, the term “module” refers tofunctions that can be implemented in hardware, software, firmware, orany combination of one or more thereof. As utilized herein, the term“exemplary” means serving as a non-limiting example, instance, orillustration.

FIG. 1 is a perspective view of a multi-branch epicyclic differentialoutput mechanism 100, in accordance with an example embodiment of thedisclosure. As shown, the mechanism 100 includes a primary differentialassembly 102, a fore secondary differential assembly 104, and an aftsecondary differential assembly 106. The primary differential assembly102 includes a primary interface or gear 108 configured to be driven bya mechanical power source, such as a motor, via one or more gears, aclutch, a belting system, a roller chain and sprocket, or other suitablesystem. As shown, mechanism 100 provides a four-branch design, such thatmovement of the primary interface 108 drives one or more planet gears122, which in turn provide mechanical power to one or more interfaces orannular output ring gears 110, 112, 114 and 116. As shown in the severalfigures, primary interface 108 and the one or more interfaces 110, 112,114 and 116 may be configured as gears that mesh with another gear totransfer mechanical power. However, as provided herein, the severalinterfaces could be configured as one or more gears, a clutch, a beltingsystem, a roller chain and sprocket, or other suitable system.

For example, the multi-branch epicyclic differential output mechanism100 can use epicyclic gearing to selectively apply torque from theprimary differential assembly 102 between the fore and aft differentialassemblies 104, 106. As disclosed herein, the assemblies function asplanetary gears as the axes of each planet gear 122 revolves around acommon central axis (e.g., coaxial with the shaft). Further, as shown inthe several figures, when activated, each output ring gear (e.g.,interfaces 110, 112, 114 and 116) meshes with one or more rotatingplanet gears (e.g., planet gears 122A and 122B of fore and aftdifferential assemblies 104, 106, respectively) of the respective foreor aft differential assemblies 104, 106, such that an interior of eachoutput ring gear meshes with the exterior of a corresponding planetgear. For example, the multi-branch epicyclic differential outputmechanism 100 has the advantage of being relatively compact along thelength of the central axis (e.g., shaft 126 or sun gear 118), as well aslimiting the bulk of the device. Although the example of FIG. 1 isillustrated as a four-branch design, fewer or more than four outputrings are also possible. For example, each secondary differentialassembly can be configured to drive a single output ring gear or threeor more output rings by employing the concepts disclosed herein.

Additionally or alternatively, each interface 110, 112, 114 and 116 canbe employed as an input. For example, a power source can drive one ormore of the interfaces 110, 112, 114 and 116 to drive any other of theinterfaces 110, 112, 114 and 116, as well as primary interface 108. Inthis manner, application of an actuator and/or braking system, asdisclosed herein, serves to select a desired interface as an input (totransfer mechanical power from an external source to the mechanism 100)and/or an output (to transfer mechanical power from another interface toan external load).

FIG. 2 illustrates another perspective view of the multi-branchepicyclic differential output mechanism 100. As shown, a lock nut 120serves as an axial retention feature for a shaft 126 that spans from theprimary differential assembly 102, through fore secondary differentialassembly 104 and to the aft secondary differential assembly 106.

Advantageously, the disclosed multi-branch epicyclic differential outputmechanism 100 is designed to fit in a compact enclosure while providingmultiple single-axis differentials. The compact design derives fromemployment of a single common axis about which the assemblies andoutputs rotate, thereby delivering a power dense assembly configured todrive a plurality of outputs (e.g., interfaces 110, 112, 114 and 116).This compact design derives from employment of an in-line arrangement ofmultiple differentials, resulting in a relatively small number ofbearings in comparison to multiple single axis differentialarrangements. For example, in the mechanism 100, no sun gears mesh withsecondary differential planet gears (e.g., 122A, 122B) and/or themulti-functional output ring gears (e.g., output ring gears 110, 112,114 and 116). In particular, referring to FIGS. 3 and 4, the output ringgears 110, 112, 114 and 116 mesh with secondary planet gears 122A, 122Band input and/or output interfaces for a load (e.g., load 164 shown inFIG. 5).

As disclosed further below, selection of a particular output can beachieved via activation or deactivation of a braking system, groundingmechanism, or other suitable technique. For example, a configurablebrake may include electrically or mechanically configurable brakes.Electrical brakes may be actuated by applying or removing power to theirinputs, thereby engaging or disengaging the braking action. Mechanicalbrakes may be configured by mechanical force, such as by applying linearor rotational force to an input of the brakes.

In examples, the primary gear 108 that serves as an input/outputinterface (e.g., shown as a ring gear in FIG. 1) of the primarydifferential assembly 102 can be engaged or disengaged via a brake.Thus, as disclosed herein, when engaged, a corresponding sun gear willturn, causing rotation of a respective secondary differential assembly(e.g., fore secondary differential assembly 104, aft secondarydifferential assembly 106). As the one or more secondary differentialassemblies rotate, one or more planet gears (e.g., planet gears 122A,122B or planet gear assemblies) corresponding to a selected output ringgear (e.g., output ring gear 110, 112, 114, 116) can be activated byanother brake. Such selective activation allows for rotation of thesecondary differential assembly to transfer torque to the selectedoutput gear via the one or more planet gears.

In one example, the configurable brakes may include power on brakes thatare engaged by applying power to their inputs. In another example, thebrakes may include power off brakes that are disengaged by applyingpower to their inputs. The power may be applied to the brakes by one ormore control units. Thus, selection of an output and desired operationthereof, and activation or deactivation of the output via a brakingsystem, results in selective control of multiple outputs provided by thedisclosed multi-branch epicyclic differential output mechanism 100.

FIG. 3 is a lateral view of multi-branch epicyclic differential outputmechanism 100. As shown, multiple planet gears 122 are included with theprimary differential assembly 102. For example, shaft 126 can extendthrough all or a portion of the length of the multi-branch epicyclicdifferential output mechanism 100, through the primary differentialassembly 102, the fore secondary differential assembly 104 and aftsecondary differential assembly 106. In this example, a sun gear 118 isfixed or otherwise connected to the shaft 126 and configured to matewith one or more planet gears 122 of the primary differential assembly102 to drive the aft secondary differential assembly 106. Additionallyor alternatively, sun gear 141 is also configured to mate with one ormore planet gears 122 of the primary differential assembly 102 to drivethe fore secondary differential assembly 104.

In some examples, the primary differential assembly 102 includes a cageor carrier 128 with primary interface or gear 108 formed thereon in afixed arrangement, such that driving the primary interface or gear 108serves to rotate the carrier 128. The primary differential assembly 102can include one or more planet gears or planet gear assemblies 122(e.g., four planet gears 122), each configured to rotate about a planetshaft. Each planet gear 122 can include one or more spacers, such as along spacer and a short spacer, and one or more radial supports orrolling element bearings. One or more carrier radial supports or rollingelement bearings can provide support for rotational movement of theprimary differential assembly 102. Further, one or more carrier shaftradial supports can provide rolling element bearings for rotationalmovement of the shaft 126.

In some examples, the fore secondary differential assembly 104 includesa cage or carrier 142 configured to mate with one or more planet gears122 of the primary differential assembly 102 via sun gear 141. Foresecondary differential assembly 104 similarly includes multiple planetgears or planet gear assemblies 122A, to rotate about one or more planetshafts. Output interfaces 110 and 112 are configured to be driven by theone or more planet gears 122A, and supported by radial gear supports.One or more gear retaining rings and/or bearing retaining rings may alsobe employed.

Additionally, as shown, aft second differential assembly 106 containscomponents similar to the fore secondary differential assembly 104,including a cage or carrier 152 configured to accept the shaft 126, suchas via a port.

FIG. 5 is a perspective view of an assembled multi-branch epicyclicdifferential output mechanism 100 arranged to receive power from amechanical power source 154 (e.g., a motor) via a power transmissionsystem, for example, including one or more gears 156, 158. In anexample, the motor 154 may include an electrical, hydraulic, orpneumatic motor. In the case of electric motors, it may include abrushless DC motor, brushed DC motor, AC induction motor, or steppermotor, although other motors may be utilized based on available spaceand power requirements, for example. In some examples, othertransmissions may be employed, such as a clutch, belting system, orother systems or methods of transferring power from a power source.

As shown, one or more output shafts 162 include one or more gears 164configured to mate with an output ring gear 110, 112, 114 or 116 of themechanism 100, as disclosed herein. Thus, as the power source 154 drivesthe primary differential assembly 102, which causes one or more of thegears 164 to turn, an output is generated for one or more flexibletorque shaft interfaces 160A through 160D, for example.

As disclosed herein, multiple output ring gears (e.g., output ring gear110, 112, 114 or 116) can be selectively controlled to generate torquefor a corresponding output (e.g., interfaces 160A through 160D). Inoperation, each output gear is controlled by a corresponding actuator(e.g., an electromechanical actuator), which may be individually enabledby the individual actuation of a control mechanism, such as a brake(e.g., through grounding). Thus, activation or deactivation of acorresponding actuator controls the supply of torque to a selectedoutput ring gear through the mechanism 100 from the motor 154. Whilefour outputs are shown in some examples, any number of outputs andcorresponding actuators may be used depending on the differentialgearing utilized and number of outputs desired, for example.

By contrast, conventional single-axis differential gearing is limited toa two-branch design. For example, a two-branch, speed summingdifferential gearing system can include a carrier or cage that is fixedto a differential input. The cage carries a set of intermeshing planetgears, which may be arranged in pairs. At the center of such anassembly, two sun gears mesh with corresponding planet gears. Each ofthe two sun gears are rigidly linked to a corresponding branch output,resulting in a two-branch differential. The carrier, planet gears andsun gears may be supported radially on one or more rolling elements,such as bearings or bushings. To configure the carrier to drive multiplebranch outputs, multiple two-branch single-axis differential gearingmodules must be used. Further, such modules must be modified toaccommodate the desired number of multiple branches in a parallelarrangement. The resulting device has a large envelope and increasedweight, which makes the entire packaging ineffective or impractical fora variety of applications (e.g., aerospace).

FIG. 4 illustrates a schematic of a four output branch differential geartrain of an epicyclic gear mechanism 100, in accordance with an exampleembodiment of the disclosure. For example, as the primary gear 108 isdriven by a power source, one or more of the planet gears 122 within theprimary differential assembly 102 can be configured to drive the gear141 and carrier 142 of the fore secondary differential assembly 104. Therotational movement of the carrier 142 thereby turns one or more planetgears 122A within assembly 104 which, when activated, can turncorresponding output ring gears 110, 112.

Additionally or alternatively, one or more of the planet gears 122within the primary differential assembly 102 can be configured to drivethe gear 118 and carrier 152 of the aft secondary differential assembly106 by rotation of the shaft 126. For example, rotational movement ofthe shaft 126 drives the carrier 152, causing one or more planet gears122B to turn. Similarly, when activated, the planet gears 122B can turnone or both of corresponding output ring gears 114, 116.

As shown in FIG. 4, the primary differential assembly 102 (e.g., a maincage) is configured to drive two or more intermeshing planet gears 122,while being fixed to a differential input. In other words, the planetgears 122 mesh with corresponding sun gears 118, 141, which are linkedto the fore and aft secondary differential assemblies 104, 106. Sun gear118 within the primary differential assembly 102 is linked to the aftsecondary differential assembly 106 through rigid shaft 126. The aftsecondary differential assembly 106 then interfaces with the shaft 126through an anti-rotation feature, such as a spline, square and/or a hex.The shaft 126 guides the aft secondary differential assembly 106, whichis secured thereto with a lock nut 120 (see, e.g., FIG. 3).

Sun gear 141 is arranged within the interior of the primary differentialassembly 102. As shown, sun gear 141 is rigidly linked to the carrier142 of the fore secondary differential assembly 104, which is thenradially supported by rolling element bearings or bushings on the rigidshaft 126. Each carrier 142 and 152 of the fore and aft secondarycarriers, respectively, contain another set of intermeshing planet gears122A and 122B, respectively, which are configured to mesh with acorresponding output ring gear 110, 112, 114, and 116, in a nestingarrangement. Each output gear 110, 112, 114, and 116 may feature aninternal gear and/or an external gear. The internal gear meshes with theplanet gears 122A and 122B, while the external gear serves as the branchexternal interface point (e.g., to drive a load mated with the externalgear). Each carrier, planet gear, sun gear, and ring gear are radiallysupported by rolling element to provide a rigid and mechanicallyefficient package, while rotating about a common central axis.

An advantage of the disclosed multi-branch epicyclic differential outputmechanism is the compact size achieved through the specific arrangementof the primary and secondary differential assemblies and the use of ringgears that feature both internal and external gears. This particulardesign approach also reduces the number of support bearings requiredversus a more traditional way of achieving multiple branch outputs, asdescribed above. The compact size of this design leads to otheradvantages when the device is integrated within a larger torquedistribution assembly, where its compact envelope and versatility ofplacement provide a significant advantage for use in constricted spaces.

FIG. 6 illustrates a schematic of an eight output branch differentialgear train of an epicyclic gear mechanism, in accordance with an exampleembodiment of the disclosure. As shown, a primary differential assembly202 is arranged in a manner similar to the mechanism 100 described withrespect to FIGS. 1-5. Thus, the primary differential assembly isconfigured to selectively drive a fore differential assembly 204 and anaft secondary differential assembly 206, as shown. In the example ofFIG. 6, each of the fore differential assembly 204 and aft secondarydifferential assembly 206 is configured to drive a plurality of tertiarydifferential assemblies 204A, 204B, 206A, 206B (e.g., two tertiarydifferential assemblies driven by each secondary differential assembly).Selection and power distribution of the mechanism illustrated in FIG. 6can be implemented via methods described with reference to themulti-branch epicyclic differential output mechanism 100.

FIG. 7 illustrates a schematic of an electromechanical actuator controlsystem for a multi-branch epicyclic differential output or gearmechanism, in accordance with an example embodiment of the disclosure.Referring to FIG. 7, there is shown control system 200 including anelectronic control unit (ECU) 201, power distribution unit (PDU) 203,input interfaces 205A-205N, actuators 207A-207N, and output interfaces209A-209N. One or more of the inputs/outputs 209A-209N or (optionally)actuators 207A-207N may connect to one or more grounding mechanisms208A-208N to engage or disengage a brake to activate a selectedinput/output interface or gear. In some examples, the inputs/outputs209A-209N are integrated with the PDU 203. In other examples, theinputs/outputs 209A-209N and/or the grounding mechanisms 208A-208N areoperably linked to the PDU 203. In some examples, selection ofinputs/outputs 209A-209N is controlled via the ECU 201, in addition orin the alternative to PDU 203, such as via grounding mechanisms208A-208N and/or actuators 207A-207N.

In accordance with the example mechanism 100 disclosed herein,inputs/outputs 209A-209N (e.g., interfaces, such as output ring gears)may be coupled to the actuators 207A-207N (e.g., electromechanicalactuators) to enable actuation, such as by engaging or disengaging abrake. The PDU 203 operates to actuate the actuators 207A-207N. Inexamples, a single PDU 203 is operable to control multiple actuators207A-207N, as opposed to each actuator containing a motor andcontroller, as with conventional systems. The combination of thedifferential gearing, electro-mechanical brakes for each output ringgear and the control unit act as an actuator selector mechanism for adesired output, as is disclosed with respect to the several drawings.

In the illustrated example, the ECU 201 may include an electroniccontrol processor operable to receive input signals from sensor(s)and/or limit switches in the actuators 207A-207N, and also receive userinputs such as from the input interfaces 205A-205D. Based on informationfrom the input interfaces, the ECU 201 may provide output signals to theactuators 207A-207N via the power distribution unit 203. The ECU 201 maybe within or coupled adjacent to the power distribution unit 203.

The electrical interfaces 205A-205D may include electronic orelectromechanical switches for indicating when an output is to beactivated or deactivated. This may include a control panel of switches,a touchscreen display, and/or discrete buttons or switches, for example.Differential gearing from the power distribution unit 203 (e.g., viaactivation of the mechanism 100) may enable multiple actuators to bedriven by a single PDU.

In order to control each output, each corresponding grounding mechanism208A-208N may include an electrically configurable brake for locking, or“grounding,” each output of the differential gearing, so that only theparticular actuator with its brake disengaged receives power to drivethe selected output 209A-209N. For example, a control system, logicsequence, and/or a user may activate a desired output. In an example, auser may press a button on a control panel coupled to or part of theelectrical interfaces 205A-205D, sending a control signal from therespective electrical interface to the ECU 201 in or coupled to thepower distribution unit 203.

In some examples, the grounding mechanism 208A-208N is activated viaactuators 209A-209N. For instance, the ECU 201 may send an electricalsignal to a selected grounding mechanism 208A-208N via a correspondingactuator of the actuators 207A-207N, which may engage a power source(e.g., motor 154 as provided in FIG. 5) of the PDU 203. The electricalsignal sent to the selected actuator may disengage a brake such that theselected differential gearing in the PDU 203 can provide power to theactivated actuator and associated output. For the example shown in FIG.5, the motor 154 may be controlled by the ECU 201, and may providetorque for the output ring gears of the mechanism 100 via the gearingsystem 156, 158. A slip clutch may be provided to limit the torque fromthe motor 154 to avoid excessive torque being provided. Gearing system156, 158 may include multiple mechanical gear components to provide agear ratio between input and output shafts (e.g., between the motor 154and differential output or gear mechanism 100) so as to step up or downthe rotational speed.

In some examples, the grounding mechanism(s) 208A-208N can beincorporated or integrated with a corresponding actuator, and arecontrolled via commands to the actuator. In additional or alternativeexamples, the grounding mechanism(s) 208A-208N are responsive tocommands directly from the ECU 201. Thus, a grounding mechanism can becontrolled directly via the ECU 201 without the use of an actuator.

The brakes may include electrically or mechanically configurable brakes.In an example, the brakes include power-off brakes that disengage withpower applied and stay engaged with no power applied. In anotherexample, the brakes include power on brakes that are engaged by applyingpower to their inputs. The power may be applied to the brakes by the ECU201. The ECU 201 may include a processor, for example, and associatedelectronics, for receiving input signals and generating output signalsto the PDU 203 based on programming stored in the ECU 201. Moreover, insome examples, a mechanical input can be used to engage and/or disengagea mechanically configurable brake.

Certain aspects of the disclosure may be found in a method and systemfor an epicyclic differential output mechanism for multiple outputs.Exemplary aspects of the disclosure may include an epicyclic gearmechanism that includes a primary differential assembly to selectivelydrive the fore secondary differential assembly and the aft secondarydifferential assembly. The fore secondary differential assemblyselectively drives one or more fore interfaces (e.g., output gears),whereas the aft secondary differential assembly selectively drives oneor more aft interfaces (e.g., output gears). Each of the primarydifferential assembly, the fore and aft secondary differentialassemblies, and the interfaces rotate about a common central axis. Theprimary differential assembly drives the fore secondary differentialassembly via a first sun gear, and drives the aft secondary differentialassembly via a second sun gear, both of which rotate about the commoncentral axis. Further, one or more actuators are to activate ordeactivate in order to drive a selected interface.

With reference to the several figures, multiple advantages are achievedthrough the innovative epicyclic gear mechanism disclosed herein. Forexample, a compact size is achieved through the specific arrangement ofthe primary and one or more secondary carriers, as well as the use ofinterfaces such as output ring gears featuring both internal andexternal gears. This particular design approach also reduces the numberof support bearings required for driving multiple outputs, compared toconventional ways of achieving multiple branch outputs as describedabove. The compact size of this design leads to other advantages, forexample, its compact envelope and placement versatility providesignificant advantages for use in constricted spaces, such asintegrating the mechanism into a larger torque distribution assembly.

While the present disclosure has been described with reference tocertain embodiments, it will be understood by those skilled in the artthat various changes may be made and equivalents may be substitutedwithout departing from the scope of the present disclosure. In addition,many modifications may be made to adapt a particular situation ormaterial to the teachings of the present disclosure without departingfrom its scope. Therefore, it is intended that the present disclosurenot be limited to the particular embodiment disclosed, but that thepresent disclosure will include all embodiments falling within the scopeof the appended claims.

What is claimed is:
 1. An epicyclic gear mechanism comprising: a foresecondary differential assembly to selectively drive one, more than one,or none of one or more fore interfaces; an aft secondary differentialassembly to selectively drive one, more than one, or none of one or moreaft interfaces; a primary differential assembly to selectively driveone, more than one, or none of the fore secondary differential assemblyand the aft secondary differential assembly, wherein the primarydifferential assembly, the fore secondary differential assembly, the aftsecondary differential assembly and each of the fore and aft interfacesrotate about a common central axis, wherein the primary differentialassembly is configured to drive the fore secondary differential assemblyvia a first sun gear, and to drive the aft secondary differentialassembly via a second sun gear; and a shaft in a fixed arrangement withthe second sun gear, wherein one or more of the planet gears within theprimary differential assembly are configured to cause rotation of theaft secondary differential assembly by driving the second sun gearcausing rotation of the shaft.
 2. The epicyclic gear mechanism of claim1, further comprising one or more grounding mechanisms, each groundingmechanisms configured to activate or deactivate a correspondinginterface in response to a command.
 3. The epicyclic gear mechanism ofclaim 1, wherein the first sun gear and the second sun gear rotate aboutthe common central axis.
 4. The epicyclic gear mechanism of claim 1,wherein the primary differential assembly comprises a primary carrierhaving a primary interface configured to transfer torque to drive one ormore of the fore or aft secondary differential assemblies in response toa mechanical input.
 5. The epicyclic gear mechanism of claim 4, whereinthe torque creates rotational movement of the primary carrier of theprimary differential assembly causing one or more planet gears withinthe primary carrier to turn, thereby causing rotation of the firstand/or second sun gear.
 6. The epicyclic gear mechanism of claim 1,wherein a fore carrier of the fore secondary differential assembly is ina fixed arrangement with the first sun gear, wherein one or more planetgears within the primary differential assembly are configured to drivethe first sun gear causing rotation of the fore secondary differentialassembly.
 7. The epicyclic gear mechanism of claim 6, wherein the forecarrier includes one or more planet gears such that the rotationalmovement of the fore secondary differential assembly about the commoncentral axis selectively causes the one or more planet gears to rotateabout a planet shaft.
 8. The epicyclic gear mechanism of claim 7,wherein the one or more fore interfaces comprises one or more fore ringgears, the one or more planet gears within the fore carrier beingconfigured to mesh with an interior gear of the one or more fore ringgears.
 9. The epicyclic gear mechanism of claim 1, further comprising anaft carrier of the aft secondary differential assembly, the aft carrierincluding one or more planet gears such that rotational movement of theshaft turns the aft carrier about the common central axis selectivelycausing the one or more planet gears to rotate about a planet shaft,wherein the one or more aft interfaces comprises one or more aft ringgears, wherein the one or more planet gears within the aft carrier areconfigured to mesh with an interior gear of the one or more aft ringgears.
 10. The epicyclic gear mechanism of claim 9, wherein theinterfaces are configured to be driven by one or more of a gear, a belt,or a roller chain and sprocket.
 11. An epicyclic gear mechanismcomprising: a primary differential assembly comprising: a plurality ofplanet gears to transmit motion to one, both or none of a first or asecond sun gear; and a primary carrier with a fixed primary gear, theprimary gear configured to transfer torque from a power source to theplurality of planet gears, wherein the first sun gear and the second sungear are arranged within the primary carrier; a fore secondarydifferential assembly selectively driven by torque via the first sungear and configured to selectively drive one, more than one, or none ofone or more fore interfaces; and an aft secondary differential assemblyselectively driven by torque via the second sun gear and configured toselectively drive one, more than one, or none of one or more aftinterface.
 12. The epicyclic gear mechanism of claim 11, wherein theprimary differential assembly, the fore secondary differential assembly,the aft secondary differential assembly, each of the fore and aftinterfaces, and the first sun gear and the second sun gear rotate abouta common central axis.
 13. The epicyclic gear mechanism of claim 11,further comprising a plurality of actuators to selectively activate ordeactivate one or more interface wherein a selected actuator engages abraking system corresponding to the selected interface.
 14. Theepicyclic gear mechanism of claim 13, further comprising an interfaceselection device, wherein selection of a given interface activates acorresponding actuator to drive or be driven by the selected interface.15. The epicyclic gear mechanism of claim 13, wherein the braking systemcomprises one or more of a grounding mechanism, an electricallyconfigurable brake or a mechanically configurable brake, wherein theelectrically configurable brake is actuated by application or removal ofpower to the electrically configurable brake, thereby engaging ordisengaging the configurable brake, and wherein the mechanicallyconfigurable brake is actuated by application or removal of a mechanicalforce including a linear force or a rotational force.
 16. An epicyclicgear mechanism comprising: a fore secondary differential assembly toselectively engage one, more than one, or none of one or more foreinterfaces; an aft secondary differential assembly to selectively engageone, more than one, or none of one or more aft interfaces; and a primarydifferential assembly to selectively engage one, more than one, or noneof the fore secondary differential assembly and the aft secondarydifferential assembly, wherein an interface of the one or more fore oraft interfaces is configured to selectively receive mechanical powerfrom a power source and transfer mechanical power to drive one or moreof the other fore or aft interfaces, and wherein the primarydifferential assembly, the fore secondary differential assembly, the aftsecondary differential assembly and each of the fore and aft interfacesrotate about a common central axis.
 17. The epicyclic gear mechanism ofclaim 16, wherein the other fore or aft interfaces transfers mechanicalpower to an external load, and wherein the interface of the one or morefore or aft interfaces is configured to drive a primary interface of theprimary differential assembly.